Ardipithecus ramidus, nicknamed Ardi, is arguably the most significant fossil find in the history of paleoanthropology due to its completeness and antiquity – 4.4 M. years, just 1.6 M. years after the last common ancestor with Chimpanzees. The theoretician of the group, Owen Lovejoy hypothesized that the reduction in the size of the male canine teeth and the near equal sizes of males and females was an indication of reduced male aggression and monogamy. Lovejoy pointed out that apes had been going extinct due to deteriorating climates, but also declining birth rates, and that monogamy is an efficient method to boost birthrates. The energy formerly spent by males competing for females would have been put to good use assisting with the provisioning of their pair bonded female mates and offspring.
Lovejoy reasoned that this transformation occurred by means of sexual selection. First conceived by Charles Darwin, sexual selection, exemplified by the peacock’s tail, occurs when the females of a species (mainly birds) are selected for the ability to select a trait in males. Once this process is initiated, the offspring of this increasingly selective mating produces ever stronger capacities in daughters to select certain male traits, and ever more pronounced expressions of these (“sexy”) traits (in this case lowed aggression and monogamy) in males.
Lovejoy has been criticized because he published the same hypothesis in 1981 on the basis of other early hominids. Clearly the eminent paleoanthropologist, Tim White and his distinguished team of experts, who had poured over this fossil find in secret for a decade, believe that Lovejoy got it right the first time and that Ardi only strengthened his case.
E.O.Wilson makes the calculation in his co-authored book, The Superorganism, that the world total biomass of humans and ants are about equal. Clearly there are many commonalities in the reasons for the success of the “eusocial” insects (ants, wasps, bees, etc.) and humans. In light of these similarities, Lovejoy’s monogamy hypothesis got a shot in the arm from a study by William Hughes in May of 2008 in which he analyzed the ancestral lineages of eusocial insects and found that, no matter how odd their mating patterns ended up including social systems with sterile castes, that all of them started out monogamous. So, perhaps, as much as we humans have strayed, that does not mean that our success is not based on the monogamy forged by the founding mothers of our hominid Family.